It is a question that his been asked for thousands of years.
Different peoples throughout the ages have had wonderful legends to explain the brilliant transformation of leaves in the fall. One Native American legend told the story of hunters in the sky who slew the constellation of the Great Bear every fall. The Bear's blood dripped down from the sky onto certain leaves, turning them red. Fat that escaped from the hunters' giant kettle as they cooked the Bear came down to earth and touched some of the trees, turning them yellow.
The authors of the Great Bear legend must have sensed a truth that was discovered long after the origin of their story. We know now that red leaves and yellow leaves are created from different elements and from two different processes.
Leaves change color because of chemical changes that occur in a tree as it prepares for winter. This may not be as romantic of an explanation, but it has its own mystery and, of course, the same dramatic results.
The yellows and oranges you will see this fall have been in the leaves from the day they first emerged in the spring. These' pigments are xanthophyll (yellow) and carotene (orange), and they are hidden from view by the dominant green chlorophyll throughout the summer.
But as the shorter days and cooler temperatures progress, the food-making process in the leaves declines, slowly
breaking down the light and temperature dependent chlorophyll until it disintegrates, leaving the less dominant yellows and oranges to show through.
These yellow and orange pigments are the same kind that can be found and are dominant in corn, carrots, daffodils and other yellow or orange fruits, vegetables and flowers. You may also see them in the first leaves of early spring, when less light and cooler temperatures still prevail, and it is too early for chlorophyll to be produced at regular strength.
Red leaves are a different story. The bright reds and deep scarlets you will be seeing this fall were not present in the leaves until recently, nor will you see red in every tree. While all trees have the yellow and orange pigments in their leaves, only certain species are capable of producing red.
Reds are produced by a pigment called anthocyanin, which is produced by the presence of sugar. Anthocyanin is the same pigment that makes apples, cranberries, cherries and other-fruits red, and it also gives purple and blue to grapes, blueberries and plums.
As the leaf begins to die and the chlorophyll disintegrates, veins going into and out of the leaf begin to clog and sugar produced during photosynthesis gets trapped in the leaves. When the sun's rays hit the trapped sugar in the leaves of some species of trees, anthocyanin is produced and red becomes the dominant color.
Why are the colors of some falls so much more intense than those of other falls?
Environmental conditions, such as weather, determine the brilliance of the colors. Colors are usually best with days that are dry, clear, sunny and cool. Red colors are best with sunny days, and nights that go below 45 degrees Fahrenheit without freezing. An early heavy rain or heavy winds can take the leaves off trees prematurely, making for a duller fall.
But as more is learned about the fall change of colors, the importance of each individual tree's situation becomes evident also. How much light, oxygen, nitrogen and water each tree gets will determine the brilliance of individual colors.
One tree can not only have many different colors of leaves, but different colors in each leaf. A tree partly shaded by another tree or a tall building will have different amounts of light exposure producing color variations in each area. Difference and brilliance of pigmentation in one tree can also depend on the concentration of minerals that occurs in each leaf. Individual soil conditions can determine mineral content and chemistry, also affecting color.
In addition to these variables, yellows, oranges, reds, golds and scarlets, can mix in infinite ways. Enjoy the beauty, drama, mystery. and many colors of fall!
Soil conditions are excellent for lawn work in the fall. And fall is the time to prepare soil for the long winter ahead and a healthy start next spring. This fall, your lawn may have special needs common to this time of year, such as the following:
 | Extra Watering |
| Overseeding |
| Fertilization |
| Pesticides or other disease control |
Before having any of this work done however, you can get the most out of your efforts by having your soil core aerated.
Core aeration mixes the soil with air, giving it needed oxygen, and loosens the soil giving it pockets of air or spaces in which nutrients and other lawn treatments may be received. Without aeration, the soil remains compacted and will not take in water fertilizer, seeds or pest treatments as well as it could otherwise.
Core aeration has the added benefit of breaking up thatch - the matted layer of partly decayed leaves, twigs and other debris that builds up between your soil and grass.
This fall, why not get the most from your lawn maintenance? Aerate first.
"Nature's peace will flow into you as sunshine flows into trees. The winds will blow their freshness into you... while care will drop away from you like the leaves of autumn. -- John Muir
This information is provided as a public
service by Alan Horticultural Enterprises, a full-service landscape management company.
Although we've been in business 20 years and service over 80 multifamily properties, we
maintain personal, one-on-one relationships with all of our clients to ensure customer
satisfaction. We are an environmentally conscious company, using EPA-approved products to
maintain healthy lawns that are beneficial for humans, pets and wildlife. If we can help
you with your lawn needs or questions, please call us at 630-739-0205.
ALAN HORTICULTURAL ENTERPRISES, INC.